Semiconductor device and fabrication method thereof

Abstract

This invention provides a semiconductor device having high operation performance and high reliability. An LDD region 707 overlapping with a gate wiring is arranged in an n-channel TFT 802 forming a driving circuit, and a TFT structure highly resistant to hot carrier injection is achieved. LDD regions 717, 718, 719 and 720 not overlapping with a gate wiring are arranged in an n-channel TFT 804 forming a pixel unit. As a result, a TFT structure having a small OFF current value is achieved. In this instance, an element belonging to the Group 15 of the Periodic Table exists in a higher concentration in the LDD region 707 than in the LDD regions 717, 718, 719 and 720.

1. A display device comprising:
 a first transistor comprising a channel formation region, a source region, a drain region, an insulating layer over the channel formation region, and a gate electrode over the insulating layer; 
 a first line electrically connected to the gate electrode through a second transistor; and 
 a second line electrically connected to one of the source region and the drain region, the second line being arranged substantially parallel to the first line, 
 wherein the second line overlaps with a region, in which a portion of the insulating layer and a first portion of the gate electrode extended from a second portion of the gate electrode overlapping with the channel formation region are overlapped with each other. 
 
     
     
       2. The display device according to  claim 1 , wherein the first transistor is a p-channel TFT. 
     
     
       3. The display device according to  claim 1 , wherein the first transistor has a triple-gate structure. 
     
     
       4. The display device according to  claim 1 , wherein the display device is an EL display device. 
     
     
       5. An electric appliance device having the display device according to  claim 1 , wherein the electric appliance device is one selected from the group consisting of a video camera, a digital camera, a projector, a projection TV, a goggle type display, a head-mount display, a navigation system, an audio reproduction apparatus, a notebook type personal computer, a game machine, a portable information terminal, and an image reproduction apparatus equipped with a recording medium. 
     
     
       6. A display device comprising:
 a first transistor comprising a semiconductor layer, an insulating layer over the semiconductor layer, and a gate electrode over the insulating layer; 
 a first line electrically connected to the gate electrode through a second transistor; and 
 a second line electrically connected to the semiconductor layer, the second line being arranged substantially parallel to the first line, 
 wherein the second line overlaps with a portion of the gate electrode. 
 
     
     
       7. The display device according to  claim 6 , wherein the first transistor is a p-channel TFT. 
     
     
       8. The display device according to  claim 6 , wherein the first transistor has a triple-gate structure. 
     
     
       9. The display device according to  claim 6 , wherein the display device is an EL display device. 
     
     
       10. An electric appliance device having the display device according to  claim 6 , wherein the electric appliance device is one selected from the group consisting of a video camera, a digital camera, a projector, a projection TV, a goggle type display, a head-mount display, a navigation system, an audio reproduction apparatus, a notebook type personal computer, a game machine, a portable information terminal, and an image reproduction apparatus equipped with a recording medium. 
     
     
       11. A display device comprising:
 a first transistor comprising a channel formation region, a source region, a drain region, an insulating layer over the channel formation region, and a gate electrode over the insulating layer; 
 a first line electrically connected to the gate electrode through a second transistor; and 
 a second line electrically connected to one of the source region and the drain region, the second line being arranged substantially parallel to the first line, 
 wherein the second line overlaps with a region, in which a portion of the insulating layer and a first portion of the gate electrode extended from a second portion of the gate electrode overlapping with the channel formation region are overlapped with each other, 
 and 
 wherein the channel formation region includes nickel. 
 
     
     
       12. The display device according to  claim 11 , wherein the first transistor is a p-channel TFT. 
     
     
       13. The display device according to  claim 11 , wherein the first transistor has a triple-gate structure. 
     
     
       14. The display device according to  claim 11 , wherein the display device is an EL display device. 
     
     
       15. An electric appliance device having the display device according to  claim 11 , wherein the electric appliance device is one selected from the group consisting of a video camera, a digital camera, a projector, a projection TV, a goggle type display, a head-mount display, a navigation system, an audio reproduction apparatus, a notebook type personal computer, a game machine, a portable information terminal, and an image reproduction apparatus equipped with a recording medium. 
     
     
       16. A display device comprising:
 a first transistor comprising a semiconductor layer, an insulating layer over the semiconductor layer, and a gate electrode over the insulating layer; 
 a first line electrically connected to the gate electrode through a second transistor; and 
 a second line electrically connected to the semiconductor layer, the second line being arranged substantially parallel to the first line, 
 wherein the second line overlaps with a portion of the gate electrode, and 
 wherein the semiconductor layer includes nickel. 
 
     
     
       17. The display device according to  claim 16 , wherein the first transistor is a p-channel TFT. 
     
     
       18. The display device according to  claim 16 , wherein the first transistor has a triple-gate structure. 
     
     
       19. The display device according to  claim 16 , wherein the display device is an EL display device. 
     
     
       20. An electric appliance device having the display device according to  claim 16 , wherein the electric appliance device is one selected from the group consisting of a video camera, a digital camera, a projector, a projection TV, a goggle type display, a head-mount display, a navigation system, an audio reproduction apparatus, a notebook type personal computer, a game machine, a portable information terminal, and an image reproduction apparatus equipped with a recording medium. 
     
     
       21. The display device according to  claim 1 , wherein a capacitance is generated in the region. 
     
     
       22. The display device according to  claim 11 , wherein a capacitance is generated in the region.